Methods have been disclosed to make printing inks suitable for printing either contact lenses or the molds that are then used to make contact lenses. For example, U.S. Pat. No. 4,668,240 to Loshaek discloses colored contact lenses produced by providing a contact lens constructed of polymer and coating at least a portion of the lens with coloring substance, a binding polymer having functional groups, and an additional compound having at least one of —NCO or epoxy.
U.S. Pat. No. 4,857,072 to Narducy, et al. discloses a method for making colored hydrophilic contact lenses. At least a portion of the surface of the lens is coated with a color coat comprising at least one pigment, binding polymer having functional groups, and an additional compound having at least two groups per molecule of —NCO.
U.S. Pat. No. 5,272,010 to Quinn discloses a method for preparation of colored contact lenses similar to that of those above except that an isocyanate compound is not required. Instead, adhesion promoters such as hexamethoxymethylmelamine are used.
However, all the above methods involve complex chemistry and result in a lens that requires extraction following the printing operation to remove unwanted residual compounds from the ink. If not extracted, such compounds would, at a minimum, cause irritation and discomfort when in contact with bodily tissue. The extraction process can be expensive and time-consuming and carries all the disadvantages of an additional step in any manufacturing process.
U.S. Pat. No. 6,162,844 to Lally, et al. teaches introducing at least one polymeric dye and polyvinyl alcohol into a mold, and crosslinking or polymerizing to form a lens. Likewise, U.S. Pat. No. 6,149,842 to Lally, et al. teaches the making of a tinted lens by mixing a metal phthalocyanine dye or pigment with polyvinyl alcohol, which is then dispensed into a lens mold and crosslinked or polymerized to entrap the dye or pigment within the polymeric network of the lens. However, while neither method requires extraction after printing, both result in a lens with dye or pigment dispersed throughout the lens, not an image printed on the surface or within the lens.